High pressure heat exchanger



c. P. KERR 2,133,249

2l Sheets-Sheet l fr/////f//////////// NVENTOR. Phllll sKelfrl AORNEY.

Cglrle:

Oct. 11, 1938.

HIGH PRESSURE HEAT EXCHANGER Original Filed July 14, 1933 c. P. KERR2,133,249

HIGH PRESSURE HEAT EXCHANGER Original Filed July 14, 1935 2 Sheets-Sheet2 Oct. 11, 1938.

19 INVENTOR. Bhorleslphllhps Karr ATTNEY.

Patented ct, 11, 1938 f l y UNITED STATES PATENT ,OFFICEv HIGH PRESSUREHEAT EXCHANGER l Charles Phillips Kerr, Washington, D. C., assigner toE. I. du Pont de Nemours & Company, Wilmington, Del., a corporation ofDelaware Application July 14, 1933, seaiNo. 680,356 Renewed April 19,1938 6 Claims. (Cl. 257-224) This invention lrelates to heat exchangersThere are a number of problems involved in adapted for fluids which areunder any desired theV design of heat exchange apparatus for thepressure ranging from low to extremely high transfer of heat from aliquid to a gas, for exe pressures; the apparatus herein described beingample. It is well known that on the liquid side especially useful forheating gases and their the transfer rate is affected principally by the5 l mixtures to or cooling them from high temvelocity of `the liquid andcleanliness, while peratures, under high pressures, such as arecleanliness in turn is affected by the velocity of encountered in thevarious high pressure catathe liquid. The problem, therefore, becomesone lytic synthesis processes, e. g. the synthesis of of proper spacingof the elements which con- 10 ammonia from its elements, the synthesisof alduct, for example, the gas thru the liquid. If 10 cohol from carbonmonoxide and hydrogen, etc. tubes are this medium, they must .be closeenough My apparatus is, however, readily adapted for together so thatthe cross-sectional area of the the lower temperatures and pressures andfor liquid passage around the tubes will be reduced any process oroperation where heated fluids or and a satisfactory Water velocitysecured. Unl5 their mixtures are to be used., such, for example, lessthe tubes are thus spaced close together a 15 as tubular evaporators,waste heat boilers, superhigh watervelocity cannot be obtained exceptheaters, etc. or other such heat exchange appaby the use of baiiles orsome similar expedient, ratus. and such methodsv are complex,inconvenient, The principal object of the invention is to proand haveother disadvantages, such as diicult Vide an extremely eiiicientapparatus of the assembly, leakage, high maintenance cost, etc. 20character in question. Another object is to pro- In'the construction ofsuch apparatus, therefore, vide an apparatus of such character which isit is very desirable to space the tubes or other simple, compact, andrelatively inexpensive to elements close together. construct. A stillfurther object of the inven- Where low gas pressures are handled, fairly4tion is to provide an apparatus which can be close tube or otherelement spacing can be se- 25 fabricated with ease, containing aplurality of cured by rolling the tubes or other elements into tubularmembers disposed in a relatively small a tube sheet, but this method isimpracticable space. ,These and other objects of my invention Where highgas pressures are involved. This is will be hereinafter referred to andthe novel true not so much because it is diiiicult to roll acombinations of elements whereby said objects high pressure tube into atube sheet and obtain 30k may be attained will be hereinafter more fullythereby a' joint between the tube and the sheet considered. which iskept tight, but because the resulting My invention is capable ofembodiment in tube sheet exposes a relatively large area tothe manydiierent forms, and, for. the purpose of high pressures; and any largearea under Vhigh illustration, I shall describe in the aceompanypressuredemands walls or structural members 35 ing drawings several formsofapparatus made in 0f great Strength to withstand the large aggreac'cordtherewith in which, like parts are desiggate forces developed.Consequently,I with high nated by the same characters throughout,-pressures it is essential to keep the gas con-g Figure I is a plan viewin half-section 0f one ned always in passagesof small diameter with 40modification of my apparatus, taken along preferably Small areas BXDOSedt0 the high PTGS- 40 i plane I-I of Figure II; sures.

Figure II is a cross-sectional elevation of the One feature of myinvention involves the apparatus shown in Figure I and taken along thepreparation of heat exchangers and equivalent plane 2 2 of Figure I;apparatus having passage elements or tubes Figure III is a diagrammaticplan view of a extremely close together which can be con- 45-half-section of another modification of my instructed readily and with arelatively low cost. VEHOD; I 'have foundthat this lcan be readilyaccom- Figure IV is a diagrammatic cross-sectional plished by making thetube connections to the elevation taken along the plane 4 4 of Figureheader integral with the Iheader and welding the III; l exchanger tubesproper on to the connections by 50 Figure V is a plan view of a modifiedform of bending them into positions where the Welds can header; beeasily made; by constructing the apparatus Figure VI is a diagrammaticcross-sectional in this manner the tubes can be placed as vcloseelevation Showing a plurality of the headers together as is desired. Theonly limitation on illustrated in Figure V connected by tubes. the tubespacing is the thickness of the saw or 55 aoY other machine cutternecessary for cutting out the tube segments. My manner of effecting thisconstruction will now be more fully particularized.

In Figure I, which is a half-sectional plan view of a header block whichhas been machined from a, circular block of steel, the tube connections,which will hereinafter be designated tube segments, I I, are sawed ormachined from the block after the holes I2 have been drilled. In thebase of the circular header I0 the uid conducting space I3 is machined,through this space conduits I4 lead the fluid into the holes I2 in eachtube segment. It is evident that the annular space I5, Figure II,between the two rows of tube segments II, is so small, as cut from theheader block, that it would be impossible to properly Weld enchangertubes to the segments. I accomplish this result by heating the tubesegments I I to a suitable temperature and then bending them toaposition permitting easy access as indicated in Figure II by the dottedtube segments II-A, in which position the exchanger tubes I6 may beeasily and quickly welded to them; weld shows at 26. When the exchangertubes I6 have'been welded into position the tube segments II-A are againheated, if necessary, and then with the attached exchanger tubes forcedback into their original position. By this method it will be seen thatit is immaterial how small the annular space I5 or the spaces betweenadjacent tubes are, for by my method of bending the tube segments fromposition, welding on the exchanger tubes, and then returning them totheir original position, no difficulties are encountered in obtaining aperfectly sound weld between the exchanger tubes IS and the tube:segments II. Thus tube banks can be made having tubes very closelypacked even when they are fabricated of thick walled high pressureresisting materials.

My invention, of course, is not limited to the construction of a heatexchanger, such as that described in Figures I and II, but innumerablemodifications, all of which embody the same principles of construction,are likewise within the scope of my invention.

Figures III and IV illustratediagrammatically another modification 'ofmy invention. It will be noted in the structure that the tube segmentsIl increase in height'from the periphery to the center of thecircularheader II, this being done to facilitate the attachment of theexchanger tubes. The tubes are attached in a manner analogous to thatexplained under the descriptions of Figures I and II. Tube segment II-Ais first heated and then bent away from tube segment IIB, tube segment II-B is then heated and bent away from tube segment II--C, the remainingtube segments being heated and bent successively. The

center-most tube segment IID, which need not be bent, is then welded toits exchanger tube, not shown, the exchanger tubes are then welded orotherwise attached to the tube segment adjacent to the central one andafter being attached these assembled tubes are returned, after heatingif necessary, to their normal operating position. The tube segments ofthe next succeeding row are then bent and welded to their respectivetubes and the assembled tube segments and tubes forced after heatingback into position; in succession the other tubes in the bank are weldedonto their respective tube segments and the assembly positioned in theheader block. It, of course, is immaterial fromthe standpoint ofoperability of my apparatus how the passages are made, leading to thecompleted tubes. In Figures III and IV a central conduit I6 distributesthe fluid to the conduits I4-a, III-b, I4-c and I4--d, respectively,which deliver the liquid to the correspondingly numbered tubes II-a,II-b, II-e, and II-d, respectively. y

It is to be understood that a solid header such as that shown in FigureIII may be of any desired shape, it not being necessary to have theheader in a circular form as shown in this gure. A rectangular or othershaped header can be used if desired and the tube segments machined fromit in any shape or size. It will be noted from the geometrical design ofFigure III that the machining of the various tube segments from theblock. I1 is not particularly difficult. After machining the varioussteps from the outer row of tube segments to the inner row the stepsbeing determined by the height of the rows of tubes, the rst and outerrow of tubes in each half section provlding the first and the loweststep the center row ldescribed and I have found that by machining adouble bank of tubes in a rectangular block any number of tubes may beassembled in a single bank by uniting a plurality of such blocks withoutthe difliculties attendant upon machining, casting, or otherwise formingthe individual tube segments in a one piece header block.

FigureVillustrates a rectangular block containing a double row of tubesegments. When preparing the headers in this manner the tube segmentsmay be of equal height and the fluid passage may enter the header blockI8 from any desired position therein. As indicated in this drawing thedistributing conduit I9, indicated by the dotted line in this plan view,leads the iluid to each row of the tube segments. Note the faciliitywith which the tube segments may be machined from the tube block I8 bymerely sawing thru the block I8 in the manner shown, and milling ordrilling out the triangular` pieces left after sawing thru the block inthe manner indicated.

header blocks I8-a, b, c, and I8-a1, b1, c1, similar to the blocks shownin Figure V resulting in a tubular heat exchanger having a bank ofthirty tubes. This heat exchanger is assembled by first welding a tubeto each ofthe 10 tube segments of the header block I8-a, in the mannerdescribed above, similarly welding a tube to each of the l0 tubesegments of the header block I8-a1, preparing l0 tube segments bentU-shaped, and welding each of these U-shaped segments, at each end tothe two appropriate tube segments already welded to the tube segments ofthe two header blocks IB-a and IIB-a1, thus forming a U- shapedassembly. The header block I8--b is then placed in position beside theheader block I8-a with tubes attached thereto, the other ends of whichare attached to the header block IB-bi which is positioned beside headerblock Iii-a1. In an analogous manner tubes are welded into position inblocks I8-c and I8-c1; the header blocks -|8-a, b, and c are thenclamped together as are also their corresponding header blocks |8-a1,bi, and ci. A main fluid distributing conduit 21 is provided for theadmission of fluid to the distributing conduits I9 and one 28 forwithdrawing the thermally treated fluid from the distributing conduits|91. A suitable shell 20 is then positioned about the assembled tubeswith a fluid inlet at 2| and a fluid outlet at 22. The operation of thisheat exchanger is described as an auxiliary apparatus in ammoniasynthesis. The uid, for example, a nitrogen-hydrogen gaseous mixturefrom the ammonia synthesis, passes into the distributor headers |9 andup through the thirty heat exchanger tubes 23,-during their passagethrough these tubes they give up their heat content to the-water flowingcountercurrent in the space between the tubes,-the water entering theshell 20 thru the inlet 2| and leaving the shell thru the outlet 22. Thecooled nitrogen-*hydrogen mixture then passes from the heat exchangertubes 23 in'to the headers |91 and out thru the collecting conduit 2s.

The high eiciency of a heat exchanging apparatus of this type canreadily be appreciated by the fact that the very small cavities betweenthe tubes results in an extremely high Velocity of the heat transferringfluid flowing about them, which in turn results in an exceedingly thinsurface lm outside the tubes 23 with a resulting rapid transfer of heat.In an actual operating unit which may be roughly illustrated by thediagrammatic sketchI shown in Figure VI the overall heat transfercoefiicients were found to Vary from 106 to 160 large centigrade heatunits per hour per square foot per degree centigrade, based uponthelogarithmic mean of the inside and outside surface areas of the tubesfor the ranges of temperature of gas and water used, while equipmentformerly considered to be ideal for similar purposes gave only 50 largecentigrade heat units per hour per square foot per degree centigradedetermined on a similar basis@ The surprising increase in heat transferefliciency of my apparatus is not only theoretically apparent but hasactually been demonstrated.

Figure VI illustrates a heat exchanger in which the tubes are in aU-shape which aids in compensating for expansion. It is, of course, notessential that such a shape be used, for it is immaterial to theefficiency of my apparatus whether the tubes between the headers beformed in a U-form, zigzag-form, or passed in a straight path from thelower to the upper header or any other preferred or desired shape. Anespecially efficient and remly built design adaptable to many uses isthat shown in Figures I and II; the tube segments and tubes after beingwelded together are surrounded by pipes 24 and 25, the tubes |6 beingpositioned in two circles within the annulus formed between the pipes 24and 25. One fluid is then caused to flow in the cavities about thetubes, while the other fluid is passed through the header |3distributing tubes I4 and then directly into the tubes I6.

Further examples of the flexibility of design which my invention permitsare illustrated by the many types of heat exchangers that may beconstructed about the header shown in Figure I. A heat exchanger may beconstructed, for example, which would contain any number of tubes withtwo header blocks, one above the other, for straight or zigzag tubes,or, if U-shaped tubes are to be used, one beside the other, the spaceabout the tubes being enclosed by the tube pipes 24 and V25, which, ofcourse, are straight if the k headers are placed one above the other orshaped, to the proper degree, if the U-shaped lor zigzag tubes are used.It is, of course, likewise possible that for the construction of certainheat exchange devices, evaporators, and the like, it may be foundexpedient to construct one of the headers of a given shape and the otherof another shape, for example, the lower header might well be a circularheader with a single row of tubes around its periphery and the upperheader an extended rectangular header receiving these tubes.Furthermore, in many types of construction it may be found preferable tothread the top of each tube segmentto receive a suitable threaded sectormachined into or attached to the tube or any other suitable method ofattaching the tubes may be used, although I generally prefer to effectthe connection by welding. Numerous modifications will readily suggestthemselves to the skilled engineerin this art.

While the small space about the tubes generally gives sufficiently highvelocity of the fluid in that space, nevertheless, if desired, balessuch as discs or spirals may be placed about the tubes in the space andthereby increase still further the turbulent flow of the fluid in thatspace and at the same time lower still further the surface film on theoutside of the tubes.

In a heat exchanging device in which a liquid is employed to heat orcool gas it is well known that the gas film is affected greatly by themass velocity of the gas. It is, therefore, desirable to increase thegas flow as much as is expedient, considering, among other things, thecost in pressure drop. In apparatus constructed in accord with myinvention it is permissible to go as far as desired for the tubes can bemade in a U or other form and thus theoretically any pressure dropdesired may be realized'. Another outstanding advantage coupled' withthe high efficiency and excellent flexibility of my apparatus is theease with which headers of any desired shape may be formed to fit intorestricted areas.

It is, of course, also understood that the methods of headering whichare illustrated and described are applicable not only to an arrangementin which the tube bundles are eachA enclosed in their individualjackets, such as indicated 1n Figure VI, but are equally useful inapparatus in which the tube bundle or a number of tube bundles are usedin a large shell, such as would be employed in evaporators, waste heatboilers, or other such heat exchange apparatus. In any case, by the useof apparatus designed in accord with this invention a decided advantageis derived by being able to get close tube spacing with the resultingcompact arrangement and eilcient operation.

It will be appreciated from the above description that any apparatusconstructed in accord with my invention for use in heat exchangers,evaporators, boilers, etc. and particularly when employed in highpressure synthesis equipment will come within the scope of my inventionwithout sacricing any of the advantages that may be derived therefrom.

I claim:

l. In a device for imparting heat to fluids a header block comprising aplurality ofA annular rows of tube segments integral with the headerblock and containing gas passages, the height of the tube segmentsvarying from the innermost to the outermost segment.

2. In a device for imparting heat to uids a circular header blockcomprising a plurality of annular rows of tube segments integral withand covering the face of the header block, the header block and eachsegment thereof containing a gas passage, the height of the tubesegments varying from the innermost to the outermost segment.

3. In a device for imparting heat to fluids a circular header blockcomprising a plurality of annular rows of tube segments integral withthe header block and containing gas passages, the height of the tubesegments varying from the innermost to the outermost segment on adecreasing scale.

4. In a device for imparting heat to fluids a circular header blockcomprising a .plurality of annular rows of tube segments integral withthe header block and annularly arranged on the face of the header block,the header block and each ltube segment containing a. gas passage, theheight of the tube segments varying from the innermost to the outermostsegments.

5. A device for imparting heat to fluids comprising in combination theheader block of claim 1 with tubes fixed to each tube segment.

6. A device for imparting `heat to uids comprising in combination theheader block of claim 1 with tubes fixed to the tube segments thereofwhich tubes are at their opposite ends fixed to the tube segments ofanother header block similar to the first.

CHARLES PmlLIPs Kana.`

